A stabilizer which restrains a motion of a ship is known.
As the related techniques, Patent Literature 1 discloses a stabilizer for achieving an optimal motion damping effect. In the stabilizer described in Patent Literature 1, a spring or a brake is used as a mechanism to damp the rotary motion of a gimbal. Also, in the stabilizer described in Patent Literature 1, a predetermined distance (deviation) exists between the center of gravity of the whole gimbal and the rotation axis of the gimbal. By controlling the distance (deviation), the control of a parameter which is equivalent to a spring constant is carried out.
Also, a motion reducing apparatus is described in Patent Literature 2. In the motion reducing apparatus described in Patent Literature 2, an angular velocity of the gimbal is detected by an angular velocity sensor. A control unit controls an excitation electric current supplied to an electromagnetic brake according to the angular velocity of the gimbal. By the control of the excitation electric current, the angular velocity of the gimbal is controlled.
Also, a stabilizer is described in Patent Literature 3. In the stabilizer described in Patent Literature 3, an oil type damper is used as a mechanism to damp the rotary motion of the gimbal.